Calling on all gurus of yotatech, knowers of everything Toyota

On the tail end of my 3.4 swap (99 Tacoma 5spd to 90 Pickup SR5 5spd, cruise, abs, no A/C) and have run into a problem getting it to run. When I crank the engine it immediately fires up but only runs for a couple of seconds and then dies or stalls. When the engine starts it sounds normal and sounds like it's running on all 6. It doesn't seem to sputter and die but rather acts almost like it was turned off. Sometimes it sounds like there's the occasional slight backfire sound when it's stalling.

After searching the forums I've tried different things but so far no luck.
So far I have tried the following:

- Power to Fuel Pump. I have cut the wire on pin 4 of the original COR relay and pinned it to FC on the ECU. I have patched in a test bulb to the circuit and the light goes on when the engine is cranked but goes out just before it dies. When I saw this I bypassed the relay bu running a jumper wire to +12v and verified the pump was working (could hear fuel pump running, fuel flowing, and the test light stayed on). Left the jumper connected with the pump running and tried to start. (No Change) Fuel pump and filter are new. Unable to check Fuel Pressure (Can't find connector).

- IGF: Ran a continuity test on the wire from the connector on the ignitor end to the ECU. It checked out. Also patched in a bypass test wire from the connector on the ignitor end to the ECU (IGF) just in case. Cranked the engine and still (No Change)

- Have tried leaving the key in the start position letting the starter continue to run (No Change)

- Fuses: Checked all fuses & they all seem good

- Swapped EFI relay with known good unit (No Change)

- Verified MAF direction. It was in backwards and was corrected (No Change)

- Swapped MAF with another unit (No Change)

- Found vacuum hose missing on intake and corrected. (No Change)

- Verified Vacuum line to Fuel Pressure regulator is connected

- Verified VC line is getting +5v Switched at ECU

- Verified +B line on ECU is getting +12v Switched

- Verified BATT line on ECU is getting +12v and stays on when key is off (un-switched)

- VG line (Don't know what it does) it's getting +0.07v Key on and off

Check Engine light goes on when the key is on. Stays on while cranking (think this is normal) but engine doesn't run long enough for the light to go out. Don't have the ODBII reader yet so can't pull codes.

Donor engine is from a 99 Tacoma 5spd going into a 90 Pickup 5spd, Cruise, ABS, No A/C

I'm out of ideas. Hopefully you guys have some!

 

What about COR to VAFM "FC". It was II3 26 to IH1 23 on mine. Also check IGN2 to injectors. II3 8 to IH1 14 on mine.

 

Also on the wire you ran that goes to your starter solenoid, you should splice a wire off that, and it goes directly to STA on the ECU. Got that one?

 

make sure all of your ecu grounds are accounted for and grounded.

 

Checked the COR relay to FC and it is connected.
Checked IGN2 to Injectors and it is connected. Getting +12v Switched

Checked for any loose grounds on the ECU but can't find any. Checked the ECU pinout for 1999 and I don't see any specifically labeled something like GND or anything.

Tried uploading my pinout spreadsheet but it's too large even after zipping

 

Everything above are good things to check!!!

Most of the time when I read these threads, the outcome is the MAF is wrong, bad, or the wires in the plug are not making contact. Ultimately though, the computer doesnt interface with the MAF correctly and cause the instant shutdown. I would check the wires on the MAF plug for continuity and be SURE that they are seated in the plug correctly and making contact.

The other common culprit is the ignitor. The is a brown wire I believe that has been known to come out of the plug enough to not make contact but appear that its in tact. Again, I would check all the wires in that plug as well and be SURE that they are in place and correctly seated and making contact.

If those and everything that Victor and Vital said check out, I think that you are going to have to get a OBD2 reader and run the thing on ether long enough to grab a code to point something out to you. I got mine on Amazon for about $25 or so. Hooks to a laptop

If you want, email me your file and I'll try to host it and put it up for the guys to see it and maybe someone can help from that. dntsdad@me.com

 

From everything you said, it sounds like you have an incorrect power line to the ECU, like wiring a line that is supposed to be constant +12V to a switched +12V. Check all your power wires.

IIRC, the ECU has only one ground, and that goes to the OBDII connector. My memory could be misleading me though.

 

Convert spreadsheet to pic

:wabbit2:

 

So checked all wires in the MAF & Ignitor connectors and they all seem to be OK. Also ran a continuity test from the connectors to the ECU and they all seem to check out

Managed to crunch down the spreadsheet down so it's small enough upload. Had to do it one page at a time so there's 8 pages.

This spreadsheet is for 1999 Tacoma 5spd to 1990 Pickup 3.0 5spd, ABS, Cruise, No A/C

Here they are: Pages 1 -3

Page 1.pdf

Page 2.pdf

Page 3.pdf

 

Page 4.pdf

Page 5.pdf

Page 6.pdf

 

Page 7.pdf

Page 8.pdf

 

Let me know if there are any errors or corrections.
I'll like to update before I post the final copy

 

Update:

Managed to borrow an ODBII scan tool. Hooked it in and it's reporting no codes
Verified the scan tool is actually talking to the ECU and it appears to be picking up on a specific protocol. Scan tool reports no codes stored or pending. Also says MIL is off

Ran through the startup procedure and got it running long enough to verify that the Check Engine Light actually does go out once it fires but comes back on once it dies.

Side Note: The scan tool only appears to talk to the ECU if the key is on. If the key is off it reports that it can not find the ECU. Not sure if this is normal but I thought the scan tool should be able to pick up the ECU with the key on or off.

I'm pulling out my hair on this one!

 

It should interface with key on.

I think that you need that thing to run longer. Might need a can of ether to help it.

 

Finally got it to run!

Turns out it was the COR relay.
I was re-using the original relay by cutting pin 4 and hooking it to FC. It appeared to work with test lights, Fuel Pump, etc but for some reason it was causing an issue. Wired in a standard relay and it's ALIVE!

Only issue now is the new relay makes a buzzing sound when the key is on (engine running or not). Not sure why the original relay won't work but that's what was causing my grief

Thanks Guys!

 

read dntsdad's post at the top of the forum he goes over both the stock 3.0 cor and the 3.4 cor. Although from what I can remember the 3.4 cor relay is basically the same as a standard bosch relay.

 

Ya the 3.4 relay is just a standards style relay in a slimmed down case.

If its buzzing, the only thing that I can think of that would cause that is low voltage that is causing the coil to freak out, or the relay itself is bad.

If you have a good power supply (10-13volts), A GOOD GROUND (which should be the FC from the ECM so it should be good enough) then I would replace it.

You can just get a standard Bosch style relay (Bosch and Potter and Brumfield aka P&B and the highest quality and usually will last a lifetime) at your local Best Buy or similar car stereo shop.

If you have a donor vehicle, the stock COR in the Tacos and 96+ Runners are attached to the bottom of the fuse panel.

 

my problem was that i had no power to the maf sensor. it would fire up and i could almost keep it running but only for a few seconds if that.